1. Field of the Invention
Embodiments of the invention relate to onboard ignition control devices for internal combustion engines.
2. Description of the Related Art
Ignition control devices for an internal combustion engine are known to conduct multiple ignition when spark performance is degraded because of decreased battery voltage, for example.
Japanese Unexamined Patent Application Publication No. H07-103122 (also referred to herein as “Patent Document 1”) discloses an ignition control device for an internal combustion engine that conducts additional second and third ignition by repeating supplying and cutting of current at every 4 msec following an ignition at a normal ignition timing in the case of cold engine start or low water temperature.
Patent Document 1 discloses a conventional technology in which after a current supplying period of maintaining an ignition signal to command application of the battery voltage to the primary side of the ignition coil in an ON state, at least one time of combination of a discharge time and a rest time, the ignition signal being held in an OFF state in the discharge time and held in an ON state again in the rest time. Thus, multiple ignition is performed in which plural times of spark discharge occurs at a spark plug connected to the secondary side of the ignition coil, corresponding to the operating range.
In the conventional technologies disclosed in Patent Document 1 and Japanese Unexamined Patent Application Publication No. 2000-345949, the ignition device is ignited several times when the operation temperature is low or the battery voltage is low. These technologies employs a voltage-controlled type semiconductor element such as an insulated gage bipolar transistor and a power MOS field effect transistor for switching operation in the primary side of the ignition coil to control battery voltage application to the primary side of the ignition coil. The voltage-controlled type semiconductor element is ON/OFF-controlled receiving an ignition signal on the gate thereof, and when the voltage-controlled type semiconductor element transitions from an ON state to an OFF state, spark current is generated in the secondary side of the ignition coil to generate discharge at the ignition plug.
In order to produce several times of continuous spark ignition, the voltage-controlled type semiconductor element needs to repeat operations of turning OFF followed by turning ON. However, the response characteristic of the voltage-controlled type semiconductor element in the turning OFF operation may not be enough quick to follow the multiple ignition signal.